1. Field of the Invention
The present invention relates generally to the field of catheters. More specifically, the present invention relates to dilatation catheters for use in administering treatments to relieve stenotic regions or to widen tubular passage, such as the coronary artery, as well as other vessels.
2. DESCRIPTION OF THE RELATED ART
A stenosis is a region of a blood vessel which has been narrowed to such a degree that blood flow is restricted. If the stenosis is sufficiently severe, treatment is required to restore adequate blood flow.
Percutaneous transluminal coronary angioplasty (PTCA), a procedure for treating a patient having a stenosis or constricted blood region in a coronary artery, has become a widely accepted therapeutic alternative to coronary arterial bypass surgery for many patients. PTCA increases the lumen by radial expansion. The main advantage of PTCA rests in the avoidance of the immediate post-operative discomforts associated with coronary bypass surgery, and certainly in the reduction of morbidity by use of this procedure.
Performing a coronary angioplasty involves inserting a balloon catheter into the desired coronary artery, locating the balloon at the arterial stenosis and injecting a suitable fluid into tile balloon to expand the balloon, and therefore the stenosis, radially outwardly. Some balloon catheters are too flexible for direct insertion into the patient's coronary artery. Accordingly, the standard angioplasty process begins with the insertion of a guiding catheter, or sleeve into the obstructed vessel, under local anesthesia. To facilitate the introduction of the guiding catheter, and to avoid damage to the body lumen at the puncture site, a guidewire is typically used in the insertion of the guiding catheter. The guiding catheter is designed to provide a conduit through which a balloon catheter is passed.
A lesion may be approached with a guidewire by advancing the catheter and guidewire as a unit, or by advancing the guidewire first. Steering the tip of the wire is done by the surgeon or by an assistant.
Ordinary balloon catheters have a balloon fastened around the exterior of a hollow catheter tube or catheter shaft. A thin tube provides a means for connecting the balloon to a suitable fluid supply for inflating the balloon.
A continuing problem with balloon dilatation catheters is the occlusion or reduction of blood flow while the balloon is expanded in an artery. Prior balloon dilatation catheters that allow blood to flow past the balloon to the distal portion of the artery are known and described in U.S. Pat. Nos. 4,581,017, 5,090,958, and 5,160,321, all issued to Harvinder Sahota, the present applicant. Each of these patents provides an apparatus for the perfusion of blood past the dilatation balloon. As catheter shaft sizes decrease, a continued need arises to maximize the flow of blood past the balloon.